The invention is particularly well suited for a high-speed radial tire having a belt structure which consists of a pair of belt plies that are reinforced with cords made of a high modulus material, for example, brass-coated steel wires, and is designed to improve the handling and speed performance characteristics of such a tire, by avoiding deformation of the tread which generally occurs at higher speeds, and to reduce the ply steer effect, i.e. the lateral forces on the tire at zero degree slip angle. The invention is also advantageously used in tires with several or a number of belt plies which are reinforced with glass or aramid cords.
Briefly stated, the invention is in a radial tire having a belt structure comprising a pair of belt plies reinforced by cords. A carcass overlay is provided between the belt structure and carcass plies of the tire. The carcass overlay consists of a single ply with opposing marginal edges which extend laterally beyond the belt structure. The carcass overlay is reinforced with cords which extend substantially circumferentially of the tire. Further, the cords of the carcass overlay are inextensible when the tire is toroidally shaped and vulcanized, but elongatable in correlated relation to the blow-up ratio of the tire from a generally cylindrical configuration to a toroidal shape.
The expression "blow-up ratio", as used herein and in the claims, means the ratio of the overall diameters of the carcass plies, when the tire is fully molded and vulcanized in a toroidal configuration, and when the carcass plies are in a cylindrical shape on a tire building drum.